This invention pertains to reversible heat exchanger or regenerator systems used in an air separation plant for the production of, inter alia, pure nitrogen by the fractional distillation of liquefied air.
In the conventional air separation plant using a low pressure distillation cycle it is customary to remove water and carbon dioxide from the incoming air by condensing these constituents on the surfaces of a heat exchanger or regenerator. The heat exchanger (regenerator) is constructed so that the impurities condensed onto the surfaces of the exchanger can be removed by stopping the flow of the incoming air (gas) and forcing a low pressure gas through the exchanger in the reverse direction to evaporate the impurities and remove them from the plant and thus prepare the exchanger to treat incoming air. In ordinary air plants the low pressure gas is a waste product stream which is alternately cycled between several exchangers to provide continuous purging or cleaning of the surfaces of the exchanger not being used to treat the incoming air. In most instances the low pressure gas contains small quantities of air that leaks into the stream through a switch or check valve because of the pressure differential between the two streams.